the Displacement of Shore-lines. 507 



It is, further, probable that the force of viilcanicity stands 

 in relation to the changes in the eccentricity. Each of the 

 great geological formations, from the Pre-Gambrian itself, has 

 had its volcanoes (see A. Geikie, ' Textbook,' pp. 259-260) ; 

 and we have already seen that the same author states that 

 there have been periods in the earth's history when vulcanicity 

 was much more powerful and widely distributed than at other 

 times. We have seen how the upheaval of the land was accom- 

 panied by volcanic outbursts ; and as regards the Tertiary 

 period, at any rate, it appears that the great overflows of 

 the sea were followed by periods during which the solid 

 ground began to rise during violent and wide-spread volcanic 

 eruptions. 



For easy reference we will finally enumerate all the arcs 

 in the curve, and name the geological stages supposed to cor- 

 respond to them. To some extent we adopt the names given 

 by Charles Mayer Eymar*. 



LOWER TERTIARY; EOCENE. 

 Cycle I. in the curve. 



Lower Eocene. Arcs 1-6. 



From 3,250,000 years to 2,720,000 years before the 



present time. 



Arc 1. Etage Montien ? 



2. „ Heersien. 



3. „ ISuessonien. 



4. „ Ypresien inferieur ? It t • 



f- \r ' • ' • Q / Londinien. 



0. „ ipresien superieur.'' j 



6. ,, Paniselien. 



Middle Eocene. 

 From 2,720,000 to 2,150,000 years before the present time. 

 Arcs 7-12. Etage Parisien, with 6 oscillations. 



Upper Eocene. 



From 2,150,000 to 1,810,000 years before the present time. 



Arcs 13-16. Etage Bartonien, with 4 oscillations. 



* See his valuable Classification des Terrains Tertiaires (Zurich, 1884). 

 He divides his stages into tvro substages — one with " mers amples," and 

 one with ''mers basses." Some of his stages, however, represent several 

 oscillations. He thinks that the precession of the equinoxes is the cause 

 of the changes in the level of the sea. The whole of the Tertiary and 

 Quaternary periods must, according to him, have had a duration of only a 

 little over 300,000 years. He founds his views upon Schmick's untenable 

 hypothesis of the dependence of the sea-level upon the precessions. 



